Low-melting-point metal material injection molding method, and machine for practicing the method

Abstract

An injection molding machine includes a pair of injecting units. In each of the cylinder barrels of the injection units, a metal element having a melting point of 650° C. or lower, or an alloy of such metal element is melted and measured by using heat which is externally applied thereto, and frictional heat, and shearing heat which are produced when the screw in the cylinder barrel is driven.

What is claimed is: 
     
       1. A method of injection-molding a low-melting-point metal material comprising the steps of: melting a solid low-melting-point metal material in each cylinder barrel of a pair of injecting units by using heat which is externally applied thereto, and frictional heat and shearing heat which are produced when a screw in each of said cylinder barrels is rotated, said pair of injecting units communicating with a single mold cavity via sprues;   measuring said molten solid low-melting-point metal in each of said pair of said injecting units up to a predetermined quantity;   driving said screw of each of said cylinder barrels in an axial direction to inject said low-melting-point metal material into said cavity.   
     
     
       2. A method of injection-molding a low-melting-point metal material as claimed in claim 1, wherein said low-melting-point metal material is a metal element having a melting point of 650° C. or lower or an alloy containing at least one metal element having a melting point of 650° C. or lower. 
     
     
       3. A method of injection-molding a low-melting-point metal material as claimed in claim 2, wherein a sum of the volumes of said low-melting-point metal materials measured by said two injecting units (30a and 30b) is at least 5000 cc. 
     
     
       4. A method of injection-molding a low-melting-point metal material as claimed in claim 1, wherein a sum of the volumes of said low-melting-point metal materials measured by said two injecting units (30a and 30b) is at least 5000 cc. 
     
     
       5. An injection molding machine comprising: a pair of injecting units, each of said injecting units including:   a cylinder barrel having an injecting nozzle at the front end thereof;   a screw disposed in said cylinder barrel such that said screw is rotatable and axially drivable;   driving means for rotating and axially driving said screw;   a stationary board having nozzle inserting holes for receiving said injecting nozzles; and   injecting-unit supporting stands for mounting said pair of injecting units parallel to each other, said injecting-unit supporting stands being movable towards and away from said stationary board.   
     
     
       6. An injection molding machine as claimed in claim 5, further comprising: a metal mold having a cavity communicable with said nozzle inserting holes formed in said stationary board through at least two sprues.   
     
     
       7. An injection molding machine as claimed in claim 5, further comprising: a swing member on which said injecting-unit supporting stands are fixedly mounted, said swing member being swingable about a swing pin thereof.